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EP0605991A1 - Nur Basismetall enthaltender Katalysator System für Verbrennungsmotoren - Google Patents

Nur Basismetall enthaltender Katalysator System für Verbrennungsmotoren Download PDF

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Publication number
EP0605991A1
EP0605991A1 EP93310345A EP93310345A EP0605991A1 EP 0605991 A1 EP0605991 A1 EP 0605991A1 EP 93310345 A EP93310345 A EP 93310345A EP 93310345 A EP93310345 A EP 93310345A EP 0605991 A1 EP0605991 A1 EP 0605991A1
Authority
EP
European Patent Office
Prior art keywords
catalyst
support material
base metal
stage
stage catalyst
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP93310345A
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English (en)
French (fr)
Inventor
Somasundaram Subramanian
Robert J. Kudla
Mohinder S. Chattha
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ford Werke GmbH
Ford France SA
Ford Motor Co Ltd
Ford Motor Co
Original Assignee
Ford Werke GmbH
Ford France SA
Ford Motor Co Ltd
Ford Motor Co
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Filing date
Publication date
Application filed by Ford Werke GmbH, Ford France SA, Ford Motor Co Ltd, Ford Motor Co filed Critical Ford Werke GmbH
Publication of EP0605991A1 publication Critical patent/EP0605991A1/de
Ceased legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/30—Tungsten
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/19—Catalysts containing parts with different compositions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • B01D53/9477—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on separate bricks, e.g. exhaust systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • This invention is directed to a catalyst system comprising a first-stage high temperature catalyst and a second-stage lower temperature catalyst, for removing nitric oxides (NO x ), carbon monoxide (CO), and hydrocarbons (HC's) from exhaust streams of, e.g., lean-burn (less than stoichiometric amount of fuel) internal combustion engines.
  • a catalyst system comprising a first-stage high temperature catalyst and a second-stage lower temperature catalyst, for removing nitric oxides (NO x ), carbon monoxide (CO), and hydrocarbons (HC's) from exhaust streams of, e.g., lean-burn (less than stoichiometric amount of fuel) internal combustion engines.
  • a number of catalysts have been suggested to convert engine exhaust gas components like carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO x ) into other gases.
  • the first two are desirably oxidized to H2O and CO2 while the nitrogen oxides present in the exhaust gas, generally nitric oxide, are desirably reduced to N2.
  • These so called “three-way" catalysts achieve simultaneous efficient (conversion > 80%) removal of CO, HC, and NO x when the fuel mixture of an internal combustion engine is slightly “rich” in fuel, i.e., in a narrow A/F ratio range between about 14.7 and 14.4, and the exhaust gas is slightly reducing.
  • Such three-way catalysts are not efficient, however, in the reduction of NO x when engines are operated on the lean (reduced fuel) side where the A/F ratio is greater than 14.7, generally 19-27, and the exhaust gas is richer in oxygen. It is desirable, however, to operate engines on the lean side to realize a benefit in fuel economy, estimated to be in the range of 6-10%.
  • Fujitani el al. in U.S. Patent 5,041,270, suggest a lean-burn catalyst system comprising a single support having a first copper catalyst for reducing NO x to N2 in the oxygen rich environment and a second oxidation catalyst comprising noble metals like Pd loaded on a porous support composed of, e.g., alumina for converting CO and HC.
  • a lean-burn catalyst system comprising a single support having a first copper catalyst for reducing NO x to N2 in the oxygen rich environment and a second oxidation catalyst comprising noble metals like Pd loaded on a porous support composed of, e.g., alumina for converting CO and HC.
  • the use of the copper catalyst upstream of the noble metal oxidation catalyst is critical to this invention.
  • the catalyst systems described have certain disadvantages. These include: a) relatively high cost associated with the use of precious metal catalysts, b) narrow operating temperature window because of the limited temperature range over which significant NO x removal is achieved, and c) either relatively low peak NO x conversion activity (acidic alumina) or poor durability (zeolite supported catlyst of Fujitani el al.).
  • the present invention broadly relates to a catalyst for removal of NO x , CO, and HC's from exhaust gases produced, e.g., by an internal combustion engine.
  • the catalyst comprises a two-stage system comprising a first-stage catalyst and a second-stage catalyst.
  • the exhaust gas may be automobile exhaust gas and the invention is adapted to be useful in lean-burn situations, i.e., with oxygen-rich environments. In such situations, the air to fuel ratio is generally 19-27.
  • the first-stage catalyst comprises between about 0.1 and 3% by weight tungsten carried on a support material comprising mostly ⁇ -alumina.
  • the first-stage catalyst is preferably made by impregnating the ⁇ -alumina support material with a solution of a tungsten-containing compound in an aqueous or organic solvent, subsequently drying the impregnated ⁇ -alumina and later calcining it to leave a coating of tungsten or tungsten oxide on the support material.
  • the second-stage catalyst comprises base metal on support material.
  • the base metal employed is selected from the group consisting of copper, cobalt, iron and manganese, and mixtures thereof.
  • the support material comprises mostly ⁇ -alumina and the second-stage catalyst comprises between about 0.1 ane 6% by weight base metal catalyst carried on the support material.
  • This second-stage catalyst is preferably made by impregnating the support material with a solution of a base metal-containing compound in an aqueous or organic solvent, subsequently drying the impregnated support material and later calcining it to leave a coating of base metal or base metal oxide on the support material.
  • This invention is directed to a method for the purification of exhaust gases which comprises sequentially exposing the two-stage exhaust gas catalyst system disclosed above to exhaust gases of, e.g., an internal combustion engine.
  • This two-stage catalyst system widens the operating temperature window for NO x removal and eliminates the need for noble metal catalysts.
  • This invention is directed to a two-stage system for the purification of exhaust gases containing nitrogen oxides, carbon monoxide, and hydrocarbons. It is particularly suitable for use with lean-burn internal combustion engines, such as automotive engines.
  • the exhaust temperature of the lean-burn engine depends on several factors, including A/F ratio, amount of exhaust gas recycled, spark advance used, and throttle valve position.
  • the catalyst temperature depends on its location, i.e., the distance from the exhaust manifold.
  • the first-stage catalyst is placed close to the engine manifold (Fig. 1). It takes advantage of the warmer conditions and converts, primarily in the 400 to 700C range, NO x to N2 based on its ability to catalyze the reaction between NO x and propane (C3H8) in the presence of O2.
  • Oxygen is a substantial component of the exhaust gas stream of lean-burn engines because lean-burn systems add more oxygen into the A/F mixture than is required for the complete combustion of the fuel. It also converts a portion of the HC's present to CO, CO2, and H2O and a portion of H2 to H2O. Partial conversion of CO to CO2 also occurs.
  • the second-stage catalyst is placed further from the manifold (Fig. 1).
  • the base metal catalyst is also highly effective in desirably oxidizing unreacted HC and CO to CO2 and H2O.
  • CO and H2 are present in the exhaust of a lean-burn engine and CO is produced by the NO x and C3H8 reaction over the first catalyst.
  • the result of the system is the near quantitative conversion of hydrocarbons (HC), CO and H2 to CO2 and H2O. Under this system, NO x conversions exceeding 91% were observed while simultaneously removing HC and CO.
  • the first-stage catalyst comprises mostly ⁇ -alumina as a support material carrying tungsten or tungsten oxide.
  • the support material is loaded such that the amount of tungsten is between 0.1 and 3% by weight of the entire catalyst (i.e., tungsten supported on alumina).
  • the tungsten is generally provided on the support by impregnating the ⁇ -alumina support material with an aqueous or organic solution of a tungsten-containing compound.
  • a tungsten-containing compound examples include ammonium metatungstate, metatungstic acid, tungstyl acetylacetonate, and tungsten hexahalides. Particularly preferred is ammonium metatungstate.
  • Any tungsten-containing compound which is soluble in an aqueous or organic solvent and whose functional group is capable of being decomposed by heat to leave only tungsten or its oxide on the support material may be employed in this invention.
  • Other tungsten compounds useful in this in addition to those listed above, will be apparent to those skilled in the art in view of this disclosure.
  • the tungsten compound is dissolved generally by simply mixing the compound into an aqueous or organic solvent to make a solution thereof.
  • solvents are water, dilute solutions of acids and alkalis, alcohols, toluene, isopropyl alcohol, acetone, methylethylketone, butylacetate, and dimethylformamide.
  • a solution of the tungsten compound is made as described above and is generally further diluted for impregnation.
  • the catalyst solution may also comprise a mixture of compatible solvents and/or compatible tungsten compounds.
  • the dissolved tungsten compound is subsequently provided on a support material, which comprises mostly alumina.
  • This support material is particularly preferred because it has high surface area, good adhesion and low tungsten/support chemical interaction.
  • ⁇ -alumina is meant that the support material comprises more than about 50% by weight, more preferably greater than 80%, and most preferably substantially all ⁇ -alumina.
  • the support may comprise other refractory materials like barium oxide, cerium oxide, lanthanum oxide, zirconium oxide, a-alumina, and titanium oxide.
  • “Support” is used herein to mean a material having a high surface area per unit volume and a good adhesion for catalyst applied thereto; “carrier” is used herein to mean the aggregation of support and catalytic compound excluding the carrier.
  • a mechanical carrier is preferably comprised of a monolithic magnesium aluminum silicate structure (i.e., cordierite), although its configuration is not critical to the catalyst of this invention.
  • the volume of the structure is measured by its exterior dimensions. It is preferred that the micropore volume of the silicate material be relatively low and the macropore volume provided by pores of diameter greater than 2000 angstroms be at least about 90%.
  • the surface area of the carrier should be maximized consistent with pressure drop limitations for the particular application of the catalytic system of this invention. It is preferred that the surface area of the monolithic structure provide 50-1000 meter square per liter structure, as measured by N2 adsorption. Cell density should be maximized consistent with pressure drop limitations and is preferably in the range of 200-800 cells per square inch of cross-sectional area of the structure.
  • Coating of the support material is carried out to impart preferably 0.1-3% by weight of tungsten based on the weight of the entire catalyst (including the support).
  • the support material is generally employed in granular form, preferably has a particle size in the range of 20-100 mesh, although particle size is not critical.
  • a mixture of the granular material and solution is stirred at an elevated temperature, generally of about 75-120C to evaporate the solvent.
  • the impregnated support material is then heated to decompose and eliminate the functional group from the mixture, such as by heating to 320C for one hour and thereafter for four hours at 600C.
  • the coating may alternatively be put directly on a monolith coated with ⁇ -alumina support material.
  • the tungsten compound decomposes and forms tungsten oxide. If, on the other hand, the heating is carried out in a reducing atmosphere, the tungsten compound may be reduced to elemental tungsten. When the first-stage catalyst is placed in use, oxygen present in the exhaust gas will oxidize the tungsten to tungsten oxide.
  • the second-stage catalyst according to the present invention comprises base metal on support material such as alumina.
  • the support comprises mainly ⁇ -alumina as hereinbefore disclosed for the first-stage catalyst support material.
  • the support may also comprise minor proportions of other oxides such as ceria, titania, zirconia, lanthana, a-Al2O3, and barium oxide.
  • the second-stage catalyst may instead, however, comprise zeolites exchanged with base metals.
  • the zeolite is ZSM-5.
  • the zeolite may also comprise, e.g., other zeolites such as L, Y, Mordenite types.
  • base metal comprises transition metals (of the Periodic Table) other than noble metals and includes such metals as copper, cobalt, iron, manganese and chromium. Metal which are characterized as transition metals would be known to those skilled in the art with reference to the Periodic Table to include such groups as 8, 1B, and 2B. Although the preferred base metal is copper, other non-noble metal transition metals and their combinations may be used. Transition metals are incorporated into the catalyst by impregnating or exchanging the support material with solutions of transition metal containing compounds. This is done to incorporate preferably 0.1 to 6% by weight of the base metal catalyst, preferably being copper, based on the weight of the entire catalyst (including the support). Examples of such compounds, as will be apparent to those skilled in the art in view of the present disclosure, include base metal nitrates, acetates, sulfates, acetylacetonates, and amine chlorides.
  • copper is hereinafter used as an exemplary base metal provided on ⁇ -alumina support material.
  • the copper is generally provided on the support by impregnating the support material with an aqueous or organic solution of a copper-containing compound.
  • the support material is generally employed in granular form, and preferably has a particle size in the range of 20-100 mesh, although particle size is not critical.
  • Exemplary of such copper compounds are copper nitrate, copper acetate, copper sulfate, copper hexamine chloride, copper (II) amine nitrate, copper acetylacetonate, copper (II) tartrate.
  • Particularly preferred copper compounds are copper acetate and copper nitrate.
  • Any copper-containing compound which is soluble in aqueous or organic solvent and whose functional group is capable of being decomposed by heat to leave only copper or its oxide on the support material may be employed in this invention.
  • Other copper compounds useful in this invention in addition to those listed above will be apparent to those skilled in the art.
  • the base metal may be provided on the zeolite by ion-exchange and/or impregnation as will be apparent to one skilled in the art in view of the present disclosure.
  • the base metal will be oxidized to base metal oxide in use as explained above for the tungsten catalyst.
  • the supported base metal used in the second-stage catalyst may also be provided on a monolithic carrier. The considerations pertaining to monolithic carriers provided previously (in the case of the first-stage monolithic tungsten catalyst) apply here as well.
  • the catalysts are characterized in a quartz flow reactor. Gases are blended in a manifold by means of mass-flow controllers and then routed either through a bypass line or through the reactor. The gases then flow to an analytical train for analysis. The post-catalyst gases are then analyzed to determine the extent of reaction on various constituents.
  • the catalyst used may either be in the form of a cylindrical ceramic monolith measuring 0.75 inch in diameter or be powder samples. Total gas flow over the catalyst is 3.0 litres/minute.
  • ⁇ -Al2O3 (10g, 20-40 mesh) is contacted (incipient wetness procedure) with 12 cm3 of copper acetate solution of desired concentration.
  • the resulting precursor is dried at 120C for one hour and then calcined at 500C for four hours.
  • the resulting second-stage catalyst has a Cu loading of 0.3%.
  • a sample (2.8g) of this second-stage catalyst is evaluated in the flow reactor using the following feed gas conditions: 1000 ppm NO, 40,000 ppm O2, and 2050 ppm C3H8.
  • the total gas flow rate is 3000 cm3/minute. These conditions correspond to a space velocity of 38,570 hr ⁇ 1 based on packed density of 0.6 g/cm3.
  • the redox ratio, R ratio of the reducing to the oxidizing components in the feed gas
  • R ratio of the reducing to the oxidizing components in the feed gas
  • the NO conversion is shown as a function of temperature in Fig. 2. NO conversion in excess of 30% is observed in the 500 to 540C range and a peak NO conversion of 40% is observed at 520C.
  • the CO and HC conversions are close to 100% at temperatures greater than 551C.
  • ⁇ -alumina (10g, 20-40 mesh) is contacted with 12 cm3 (incipient wetness) of aqueous ammonium meta-tungstate solution of desired concentration.
  • the precursor is dried at 120C for one hour and then calcined at 600C for six hours.
  • the resulting WO3/ ⁇ -Al2O3 first-stage catalyst has a W weight loading of 1%.
  • a sample (2.8g) of this catalyst is used in the first-bed position and a sample (2.8g) of the catalyst described in Example 1 is used in the second-bed position to form a system according to the present invention.
  • the catalyst system is evaluated using the feed gas described in Example 1.
  • the NO conversion is shown as a function of temperature in the graph of Fig. 2. From the graph NO conversion in excess of 30% is observed in the 470 to 670C range and a peak conversion of 92% is observed around 562C.
  • the catalyst temperature is lower than 500C, removal of NO x primarily occurs over the Cu catalyst. At temperatures greater than 500C, NO x removal primarily occurs over the W catalyst. In the 500-550C temperature range, both catalysts convert significant amounts of NO x to N2.
  • This W catalyst is optimally active in oxidizing hydrocarbons only at temperatures greater than 500C.
  • the presence of the Cu catalyst downstream allows HC removal at temperatures greater than 400C.
  • the HC and CO conversions approach 100% at temperatures greater than 554C.
  • Example 2 The catalyst system described in Example 2 is tested at 580C using 1000 ppm NO and 40,000 ppm O2.
  • the C3H8 concentration is varied between 400 and 3000 ppm.
  • the feed gas has O2 in excess of that required for a stoichiometric mixture.
  • the NO conversion is shown as a function of C3H8 concentration in Fig. 3. NO conversion increases with an increase in the C3H8 concentration.
  • a second-stage catalyst according to an embodiment of the present invention is made with meta-tungstic acid used in lieu of ammonium metatungstate following the procedure described in Example 2.
  • the precursor is dried at 120C for one hour and then calcined at 600C for six hours.
  • the resulting WO3/ ⁇ -Al2O3 first-stage catalyst has a W weight loading of 0.1%.
  • This catalyst is used upstream of the Cu/ ⁇ -Al2O3 catalyst described in Example 1, and the catalyst system is evaluated under conditions described in Example 2. NO conversion in excess of 30% is observed in the 467 to 634C range and a peak NO conversion of 59% is observed at 559C. The CO and HC conversions are close to 100% at temperatures greater than 546C.
  • a second-stage catalyst of the present invention is prepared from copper nitrate in lieu of copper acetate following the procedure described in Example 1.
  • the precursor is dried at 120C for one hour and then calcined at 500C for four hours.
  • the resulting Cu/ ⁇ -Al2O3 second-stage catalyst has a Cu weight loading of 0.3%.
  • This catalyst is used in downstream of the W/Al2O3 catalyst described in Example 2 and the catalyst system is evaluated under conditions described in Example 2. NO conversion in excess of 30% is observed in the 472 to 674C range and a peak conversion of 89% is observed at 565C. The HC and CO conversions are close to 100% at temperatures greater than 552C.
  • a first-stage catalyst according to the present invention is made in this example. Zirconium oxide (10g, 20-40 mesh) is contacted with 8 cm3 aqueous ammonium metatungstate solution of desired concentration. The precursor is dried at 120C for one hour and then calcined at 600C for six hours. The resulting WO3/ZrO2 first-stage catalyst has a W weight loading of 0.25%.
  • Example 2 A sample (2.8g) of this catalyst is used upstream of the Cu/ ⁇ -Al2O3 catalyst described in Example 1.
  • the catalyst system is evaluated under conditions outlined in Example 2. No conversion in excess of 30% is observed in the 469 to 668C range and a peak NO conversion of 78% at 580C.
  • the CO and HC conversions approach 100% at temperatures greater than 564C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Organic Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Materials Engineering (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Catalysts (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
EP93310345A 1993-01-07 1993-12-20 Nur Basismetall enthaltender Katalysator System für Verbrennungsmotoren Ceased EP0605991A1 (de)

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US170293A 1993-01-07 1993-01-07
US1702 1993-01-07

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WO1998039083A1 (de) * 1997-03-06 1998-09-11 Degussa Aktiengesellschaft Katalysatorsystem zur abgasreinigung von dieselmotoren
EP0605995B1 (de) * 1993-01-08 1998-09-16 Ford Motor Company Limited Zweistufiges katalysator System für einem Verbrennungsmotor
US20140127084A1 (en) * 2011-04-04 2014-05-08 Masao Watanabe Exhaust gas catalyst, method for the production of carrier, method for the production of exhaust gas catalyst, and apparatus for treating exhaust gas

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0605995B1 (de) * 1993-01-08 1998-09-16 Ford Motor Company Limited Zweistufiges katalysator System für einem Verbrennungsmotor
WO1998039083A1 (de) * 1997-03-06 1998-09-11 Degussa Aktiengesellschaft Katalysatorsystem zur abgasreinigung von dieselmotoren
EP0862940A1 (de) * 1997-03-07 1998-09-09 Volkswagen Aktiengesellschaft Mehrstufiges Dreiwegkatalysatorsystem
US20140127084A1 (en) * 2011-04-04 2014-05-08 Masao Watanabe Exhaust gas catalyst, method for the production of carrier, method for the production of exhaust gas catalyst, and apparatus for treating exhaust gas
US9617886B2 (en) * 2011-04-04 2017-04-11 Toyota Jidosha Kabushiki Kaisha Exhaust gas catalyst, method for the production of carrier, method for the production of exhaust gas catalyst, and apparatus for treating exhaust gas

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US5618505A (en) 1997-04-08

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